Method of manufacturing microstructures of metal lines

ABSTRACT

A method of manufacturing a metal line microstructure is provided. Firstly, a substrate is provided. Then, a seed layer is formed on a surface of the substrate. Then, a photoresist layer is formed on a surface of the seed layer, and a photolithography and etching process is performed to form a trench in the photoresist layer, wherein the trench has a specified width. Then, an electroplating process is performed to fill a conductive layer into the trench. Afterwards, the photoresist layer and a portion of the seed layer uncovered by the conductive layer are removed, so that the metal line microstructure is produced.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing microstructures, and more particularly to a method of manufacturing microstructures of metal lines.

BACKGROUND OF THE INVENTION

Nowadays, touch control technologies are widely applied to the touch control devices of various electronic products in order to facilitate the users to control the operations of the electronic products. For achieving the displaying function, the transparent electrode of the conventional touch panel has the transparent property and the electrically-conductive property. For example, the transparent electrode is made of indium tin oxide (ITO). As the trend of designing the touch panel is gradually toward the large-sized touch panel, the fabricating method and the structure of the transparent electrode have many disadvantages. For example, the electrical resistance is higher, the response speed is slower, more fabricating steps are required, and the fabricating cost is higher. Consequently, the ITO transparent electrodes are gradually replaced by metal lines (or metal meshes).

In comparison with the ITO transparent electrode, the metal mesh has lower electrical resistance, better electrical conductivity, faster response speed and lower fabricating cost. In accordance with the current method of manufacturing the metal line, a metal line pattern is directly printed on a substrate. As known, it is difficult to control the precision of the metal line by the printing process. In particular, it is difficult to produce the metal line with the width smaller than 5 μm by using the printing process. That is, the performance, the transparency and the line invisibility are usually unsatisfied. Moreover, it is necessary to use a stencil in the printing process. The procedure of fabricating the stencil and washing the stencil may increase the fabricating cost of the metal line. Moreover, after many printing cycles, the stencil is usually subjected to deformation and thus the printing accuracy of the stencil is deteriorated. The way of frequently replacing the stencil may increase the overall cost. Moreover, for manufacturing the metal line with the width smaller than 5 μm, the precision should be elaborately controlled. Under this circumstance, the fabricating cost is largely increased, the metal line is readily broken, and the yield is reduced. Moreover, in case that the metal line is made of silver, aluminum or copper, the metal line is possibly oxidized. The process of preventing oxidation also increases the fabricating complexity and the fabricating cost.

Therefore, there is a need of providing a method of manufacturing microstructures of metal lines in order to eliminate the above drawbacks.

SUMMARY OF THE INVENTION

The present invention provides a method of manufacturing microstructures of metal lines. By the manufacturing method of the present invention, the metal line is thinner, the fabricating cost is reduced, and the transmittance and the invisibility of the metal line are both enhanced.

The present invention also provides a method of manufacturing microstructures of metal lines in order to precisely control the line width of the metal line to be smaller than 5 μm. Consequently, the yield of the product is increased, and the oxidation of the metal line is minimized.

The present invention further provides a method of manufacturing microstructures of metal lines, in which the metal line of the visible touch zone and the wiring part of the non-touch zone of the touch panel can be simultaneously formed on the substrate in the same fabricating step. Consequently, the fabricating procedures of the touch panel are simplified, and the fabricating cost of the touch panel is reduced.

In accordance with an aspect of the present invention, there is provided a method of manufacturing a metal line microstructure. Firstly, a substrate is provided. Then, a seed layer is formed on a surface of the substrate. Then, a photoresist layer is formed on a surface of the seed layer, and a photolithography and etching process is performed to form a trench in the photoresist layer, wherein the trench has a specified width. Then, an electroplating process is performed to fill a conductive layer into the trench. Afterwards, the photoresist layer and a portion of the seed layer uncovered by the conductive layer are removed, so that the metal line microstructure is produced.

In accordance with another aspect of the present invention, there is provided a method of manufacturing a metal line microstructure. Firstly, a substrate is provided. Then, a seed layer is formed on a surface of the substrate. Then, a photoresist layer is formed on a surface of the seed layer, and a photolithography and etching process is performed to form a trench in the photoresist layer, wherein the trench has a specified width. Then, an electroplating process is performed to fill a conductive layer into the trench. Then, an anti-oxidation layer is filled into the trench and forming the anti-oxidation layer on the conductive layer. Afterwards, the photoresist layer and a portion of the seed layer uncovered by the conductive layer are removed, so that the metal line microstructure is produced.

In accordance with a further aspect of the present invention, there is provided a method of manufacturing a metal line microstructure. Firstly, a substrate is provided. Then, a seed layer is formed on a surface of the substrate. Then, a photoresist layer is formed on a surface of the seed layer, and a photolithography and etching process is performed to form a first trench and a second trench in the photoresist layer, wherein the first trench has a first width, the second trench has a second width, and the second width is larger than the first width. Then, a conductive layer is filled into the first trench and the second trench. Afterwards, the photoresist layer and a portion of the seed layer uncovered by the conductive layer are removed, so that a first metal line microstructure and a second metal line microstructure are produced.

The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A˜1E are schematic cross-sectional views illustrating a method of manufacturing microstructures of metal lines according to a first embodiment of the present invention;

FIG. 2 is a flowchart illustrating the method of manufacturing microstructures of metal lines according to the first embodiment of the present invention;

FIGS. 3A˜3F are schematic cross-sectional views illustrating a method of manufacturing microstructures of metal lines according to a second embodiment of the present invention;

FIG. 4 is a flowchart illustrating the method of manufacturing microstructures of metal lines according to the second embodiment of the present invention;

FIGS. 5A˜5E are schematic cross-sectional views illustrating a method of manufacturing microstructures of metal lines according to a third embodiment of the present invention;

FIG. 6 is a flowchart illustrating the method of manufacturing microstructures of metal lines according to the third embodiment of the present invention; and

FIG. 7 schematically illustrates the metal lines formed by the manufacturing method according to the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.

FIGS. 1A˜1E are schematic cross-sectional views illustrating a method of manufacturing microstructures of metal lines according to a first embodiment of the present invention. FIG. 2 is a flowchart illustrating the method of manufacturing microstructures of metal lines according to the first embodiment of the present invention.

Firstly, as shown in FIG. 1A and the step S20 of FIG. 2, a substrate 11 is provided. The substrate 11 is a transparent substrate, a flexible substrate or a flexible transparent substrate. Preferably, the thickness of the substrate 11 is in the range between 20 μm and 800 μm. The substrate 11 is made of polyethylene terephthalate (PET), polyetherimide (PEI), polyphenylensulfone (PPSU), polyimide (PI), polyethylene naphthalate (PEN), cyclic olefin copolymer (COC), liquid crystal polymer (LCP), glass or a combination thereof. More preferably, the substrate 11 is the flexible transparent substrate made of polyethylene terephthalate (PET). Consequently, the substrate 11 has higher impact resistance, lower brittleness and higher transmittance.

Then, as shown in FIG. 1B and the step S21 of FIG. 2, a seed layer 12 is formed on a surface of the substrate 11. In an embodiment, the seed layer 12 is produced by performing a depositing process to form a metal film on the surface of the substrate 11. For example, the depositing process is a sputtering process or an evaporation process. More preferably, the depositing process is a sputtering process. The seed layer 12 has a good electrical property and has good adsorption to the substrate 11. The seed layer 12 may be used as an interface for connecting the non-metallic substrate 11 and a conductive layer in a subsequent electroplating process. That is, the seed layer 12 may be used as a start layer of the subsequent electroplating process. The arrangement of the seed layer 12 may increase the strength and electrical property of the microstructure. Moreover, the thickness of the seed layer 12 is in the range between 5 nm and 100 nm. It is noted that the thickness of the seed layer 12 may be varied according to the practical requirements. In some embodiments, the seed layer 12 is made of metal or metal alloy. An example of the seed layer 12 includes but is not limited to a Cr/Au metal film, a Ti/Au metal film, a Ti/Cu metal film, a Cu/Cu metal film or a Ti—W/Au metal film.

Then, as shown in FIG. 1C and the step S22 of FIG. 2, a photoresist layer 13 is formed on a surface of the seed layer 12. A photolithography and etching process is performed to form a trench 14 in the photoresist layer 13, so that a portion of the seed layer 12 is exposed. That is, by the photolithography and etching process, a predetermined photomask pattern is transferred to the photoresist layer 13, and the trench 14 is formed in the photoresist layer 13. In this embodiment, the photoresist layer 13 is a wet film photoresist layer or a dry film photoresist layer, which is coated or attached on the surface of the seed layer 12. The photoresist material of the photoresist layer 13 may be a positive-type photoresist material or a negative-type photoresist material. The applications and principles of the positive-type photoresist material or the negative-type photoresist material are well-known to those skilled in the art, and are not redundantly described herein. Moreover, by changing the photomask pattern, the exposure amount, the exposure time and/or other parameters, the width and/or depth of the trench 14 may be adjusted. In this embodiment, the width of the trench 14 is in the range between 1 μm and 20 μm, preferably in the range between 1 μm and 5 μm, and more preferably smaller than 3 μm. Moreover, the depth of the trench 14 is in the range between 0.1 μm and 20 μm, and preferably in the range between 0.1 μm and 2 μm.

Then, as shown in FIG. 1D and the step S23 of FIG. 2, an electroplating process is performed to fill a conductive layer 15 into the trench 14. The conductive layer 15 is in contact with the portion of the seed layer 12 that is exposed to the bottom of the trench 14. Since the conductive layer 15 is filled into the trench 14 by the electroplating process, the formation of the conductive layer 15 is fast and the thickness of the conductive layer 15 is easily controlled. Moreover, since it is not necessary to further treat the conductive layer 15, the fabricating procedures are simplified. In some embodiments, the material of the conductive layer 15 is selected from copper, gold, silver, aluminum, tungsten, iron, nickel, chromium, titanium, molybdenum, indium, tin, or a combination thereof. In this embodiment, the thickness of the conductive layer 15 is in the range between 0.1 μm and 20 μm, preferably in the range between 0.1 μm and 2 μm, and more preferably in the range between 0.1 μm and 0.5 μm.

Then, as shown in FIG. 1E and the step S24 of FIG. 2, the photoresist layer 13 and the portion of the seed layer 12 uncovered by the conductive layer 15 (i.e. the portion of the seed layer 12 covered by the photoresist layer 13) are removed. Consequently, a metal line microstructure 16 is produced. In case that the photoresist layer 13 is the wet film photoresist layer, the photoresist layer 13 may be removed by an etching process. In case that the photoresist layer 13 is the dry film photoresist layer, the photoresist layer 13 may be removed by a stripping process. Moreover, the portion of the seed layer 12 uncovered by the conductive layer 15 is removed by an etching process, but is not limited thereto. In this embodiment, the line width of the metal line microstructure 16 is substantially equal to the width of the trench 14. That is, the line width of the metal line microstructure 16 is in the range between 1 μm and 20 μm, preferably in the range between 1 μm and 5 μm, and more preferably smaller than 3 μm. In case that the line width of the metal line microstructure 16 is controlled to be in the range between 1 μm and 5 μm (more preferably smaller than 3 μm) according to the width of the trench 14, when the metal line microstructure 16 is applied to the metal line (or metal mesh) of a visible touch zone of a touch panel, the transmittance and the invisibility of the metal line are both enhanced. In case that the line width of the metal line microstructure 16 is controlled to be in the range between 1 μm and 20 μm (more preferably in the range between 5 μm and 20 μm) the metal line microstructure 16 may be applied to the metal line of the non-touch zone of the touch panel. In other words, the metal line microstructure 16 may be used as the wiring part on the peripheral region of touch panel. The height of the metal line microstructure 16 is substantially equal to the depth of the trench 14 (e.g. in the range between 0.1 μm and 20 μm). The height of the metal line microstructure 16 may be determined according to the requirements of the impedance value, thereby increasing the stability of the metal line.

FIGS. 3A˜3F are schematic cross-sectional views illustrating a method of manufacturing microstructures of metal lines according to a second embodiment of the present invention. FIG. 4 is a flowchart illustrating the method of manufacturing microstructures of metal lines according to the second embodiment of the present invention.

Firstly, as shown in FIG. 3A and the step S40 of FIG. 4, a substrate 11 is provided. The substrate 11 is a transparent substrate, a flexible substrate or a flexible transparent substrate. Preferably, the thickness of the substrate 11 is in the range between 20 μm and 800 μm. The substrate 11 is made of polyethylene terephthalate (PET), polyetherimide (PEI), polyphenylensulfone (PPSU), polyimide (PI), polyethylene naphthalate (PEN), cyclic olefin copolymer (COC), liquid crystal polymer (LCP), glass or a combination thereof. More preferably, the substrate 11 is the flexible transparent substrate made of polyethylene terephthalate (PET). Consequently, the substrate 11 has higher impact resistance, lower brittleness and higher transmittance.

Then, as shown in FIG. 3B and the step S41 of FIG. 4, a seed layer 12 is formed on a surface of the substrate 11. In an embodiment, the seed layer 12 is produced by performing a depositing process to form a metal film on the surface of the substrate 11. For example, the depositing process is a sputtering process or an evaporation process. More preferably, the depositing process is a sputtering process. The seed layer 12 has a good electrical property and has good adsorption to the substrate 11. The seed layer 12 may be used as an interface for connecting the non-metallic substrate 11 and a conductive layer in a subsequent electroplating process. That is, the seed layer 12 may be used as a start layer of the subsequent electroplating process. The arrangement of the seed layer 12 may increase the strength and electrical property of the microstructure. Moreover, the thickness of the seed layer 12 is in the range between 5 nm and 100 nm. It is noted that the thickness of the seed layer 12 may be varied according to the practical requirements. In some embodiments, the seed layer 12 is made of metal or metal alloy. An example of the seed layer 12 includes but is not limited to a Cr/Au metal film, a Ti/Au metal film, a Ti/Cu metal film, a Cu/Cu metal film or a Ti—W/Au metal film.

Then, as shown in FIG. 3C and the step S42 of FIG. 4, a photoresist layer 13 is formed on a surface of the seed layer 12. A photolithography and etching process is performed to form a trench 14 in the photoresist layer 13, so that a portion of the seed layer 12 is exposed. That is, by the photolithography and etching process, a predetermined photomask pattern is transferred to the photoresist layer 13, and the trench 14 is formed in the photoresist layer 13. In this embodiment, the photoresist layer 13 is a wet film photoresist layer or a dry film photoresist layer, which is coated or attached on the surface of the seed layer 12. The photoresist material of the photoresist layer 13 may be a positive-type photoresist material or a negative-type photoresist material. The applications and principles of the positive-type photoresist material or the negative-type photoresist material are well-known to those skilled in the art, and are not redundantly described herein. Moreover, by changing the photomask pattern, the exposure amount, the exposure time and/or other parameters, the width and/or depth of the trench 14 may be adjusted. In this embodiment, the width of the trench 14 is in the range between 1 μm and 20 μm, preferably in the range between 1 μm and 5 μm, and more preferably smaller than 3 μm. Moreover, the depth of the trench 14 is in the range between 0.1 μm and 20 μm, and preferably in the range between 0.1 μm and 2 μm.

Then, as shown in FIG. 3D and the step S43 of FIG. 4, an electroplating process is performed to fill a conductive layer 15 into the trench 14. The conductive layer 15 is in contact with the portion of the seed layer 12 that is exposed to the bottom of the trench 14. Since the conductive layer 15 is filled into the trench 14 by the electroplating process, the formation of the conductive layer 15 is fast and the thickness of the conductive layer 15 is easily controlled. Moreover, since it is not necessary to further treat the conductive layer 15, the fabricating procedures are simplified. In some embodiments, the material of the conductive layer 15 is selected from copper, gold, silver, aluminum, tungsten, iron, nickel, chromium, titanium, molybdenum, indium, tin, or a combination thereof. In this embodiment, the thickness of the conductive layer 15 is in the range between 0.1 μm and 20 μm, preferably in the range between 0.1 μm and 2 μm, and more preferably in the range between 0.1 μm and 0.5 μm.

Then, as shown in FIG. 3E and the step S44 of FIG. 4, an anti-oxidation layer 17 is filled into the trench 14 and formed on the conductive layer 15. In an embodiment, the anti-oxidation layer 17 is an anti-oxidation metal layer. The anti-oxidation layer 17 may contain phenolic resin, photosensitive compounds, organic colored polymer dyes, inorganic colored dyes and solvent, wherein the inorganic colored dyes contains metal components. The anti-oxidation layer 17 may be black, but is not limited thereto. The arrangement of the anti-oxidation layer 17 may protect the conductive layer 15, prevent oxidation of the conductive layer 15 and avoid the color change of the metal line. Consequently, the invisibility of the metal line is enhanced.

Then, as shown in FIG. 3F and the step S45 of FIG. 4, the photoresist layer 13 and the portion of the seed layer 12 uncovered by the conductive layer 15 (i.e. the portion of the seed layer 12 covered by the photoresist layer 13) are removed. Consequently, a metal line microstructure 18 is produced. In case that the photoresist layer 13 is the wet film photoresist layer, the photoresist layer 13 may be removed by an etching process. In case that the photoresist layer 13 is the dry film photoresist layer, the photoresist layer 13 may be removed by a stripping process. Moreover, the portion of the seed layer 12 uncovered by the conductive layer 15 is removed by an etching process, but is not limited thereto. In this embodiment, the line width of the metal line microstructure 18 is substantially equal to the width of the trench 14. That is, the line width of the metal line microstructure 18 is in the range between 1 μm and 20 μm, preferably in the range between 1 μm and 5 μm, and more preferably smaller than 3 μm. In case that the line width of the metal line microstructure 18 is controlled to be in the range between 1 μm and 5 μm (more preferably smaller than 3 μm) according to the width of the trench 14, when the metal line microstructure 18 is applied to the metal line (or metal mesh) of a visible touch zone of a touch panel, the transmittance and the invisibility of the metal line are both enhanced. In case that the line width of the metal line microstructure 18 is controlled to be in the range between 1 μm and 20 μm (more preferably in the range between 5 μm and 20 μm), the metal line microstructure 18 may be applied to the metal line of the non-touch zone of the touch panel. In other words, the metal line microstructure 18 may be used as the wiring part on the peripheral region of touch panel. The height of the metal line microstructure 18 is substantially equal to the depth of the trench 14 (e.g. in the range between 0.1 μm and 20 μm). The height of the metal line microstructure 18 may be determined according to the requirements of the impedance value, thereby increasing the stability of the metal line.

FIGS. 5A˜5E are schematic cross-sectional views illustrating a method of manufacturing microstructures of metal lines according to a third embodiment of the present invention. FIG. 6 is a flowchart illustrating the method of manufacturing microstructures of metal lines according to the third embodiment of the present invention.

Firstly, as shown in FIG. 5A and the step S60 of FIG. 6, a substrate 31 is provided. The substrate 31 is a transparent substrate, a flexible substrate or a flexible transparent substrate. Preferably, the thickness of the substrate 31 is in the range between 20 μm and 800 μm. The substrate 31 is made of polyethylene terephthalate (PET), polyetherimide (PEI), polyphenylensulfone (PPSU), polyimide (PI), polyethylene naphthalate (PEN), cyclic olefin copolymer (COC), liquid crystal polymer (LCP), glass or a combination thereof. More preferably, the substrate 31 is the flexible transparent substrate made of polyethylene terephthalate (PET). Consequently, the substrate 31 has higher impact resistance, lower brittleness and higher transmittance.

Then, as shown in FIG. 5B and the step S61 of FIG. 6, a seed layer 32 is formed on a surface of the substrate 31. In an embodiment, the seed layer 32 is produced by performing a depositing process to form a metal film on the surface of the substrate 31. For example, the depositing process is a sputtering process or an evaporation process. More preferably, the depositing process is a sputtering process. The seed layer 32 has a good electrical property and has good adsorption to the substrate 31. The seed layer 32 may be used as an interface for connecting the non-metallic substrate 31 and a conductive layer in a subsequent electroplating process. That is, the seed layer 32 may be used as a start layer of the subsequent electroplating process. The arrangement of the seed layer 32 may increase the strength and electrical property of the microstructure. Moreover, the thickness of the seed layer 32 is in the range between 5 nm and 100 nm. It is noted that the thickness of the seed layer 32 may be varied according to the practical requirements. In some embodiments, the seed layer 32 is made of metal or metal alloy. An example of the seed layer 32 includes but is not limited to a Cr/Au metal film, a Ti/Au metal film, a Ti/Cu metal film, a Cu/Cu metal film or a Ti—W/Au metal film.

Then, as shown in FIG. 5C and the step S62 of FIG. 6, a photoresist layer 33 is formed on a surface of the seed layer 32. A photolithography and etching process is performed to form a first trench 34 and a second trench 35 in the photoresist layer 33, so that a portion of the seed layer 32 is exposed. That is, by the photolithography and etching process, a predetermined photomask pattern is transferred to the photoresist layer 33, and the first trench 34 and the second trench 35 are formed in the photoresist layer 33. In this embodiment, the photoresist layer 33 is a wet film photoresist layer or a dry film photoresist layer, which is coated or attached on the surface of the seed layer 32. The photoresist material of the photoresist layer 33 may be a positive-type photoresist material or a negative-type photoresist material. The applications and principles of the positive-type photoresist material or the negative-type photoresist material are well-known to those skilled in the art, and are not redundantly described herein. Moreover, by changing the photomask pattern, the exposure amount, the exposure time and/or other parameters, the widths and/or depths of the first trench 34 and the second trench 35 may be adjusted. The first trench 34 has a first width W1 and a specified depth. The second trench 35 has a second width W2 and the specified depth. The second width W2 is larger than the first width W1. In this embodiment, each of the first trench 34 and the second trench 35 is in the range between 1 μm and 20 μm. Preferably, the first width W1 is in the range between 1 μm and 5 μm. More preferably, the first width W1 is smaller than 3 μm. Preferably, the second width W2 is in the range between 5 μm and 20 μm. The specified depth is in the range between 0.1 μm and 20 μm, and preferably in the range between 0.1 μm and 2 μm.

Then, as shown in FIG. 5D and the step S63 of FIG. 6, an electroplating process is performed to fill conductive layers 35 and 36 into the first trench 34 and the second trench 35, respectively. The conductive layer 36 is in contact with the portion of the seed layer 32 that is exposed to the bottom of the first trench 34. The conductive layer 37 is in contact with the portion of the seed layer 32 that is exposed to the bottom of the second trench 35. Since the conductive layers 36 and 37 are filled into first trench 34 and the second trench 35 by the electroplating process, the formation of the conductive layers 36 and 37 will be fast and the thickness of the conductive layers 36 and 37 can be easily controlled. Moreover, since it is not necessary to further treat the conductive layers 36 and 37, the fabricating procedures are simplified. The material of the conductive layer 36 and the material of the conductive layer 37 may be identical or different. In some embodiments, each of the material of the conductive layer 36 and the material of the conductive layer 37 is selected from copper, gold, silver, aluminum, tungsten, iron, nickel, chromium, titanium, molybdenum, indium, tin, or a combination thereof. In this embodiment, the thickness of the each of the conductive layers 36 and 37 is in the range between 0.1 μm and 20 μm, preferably in the range between 0.1 μm and 2 μm, and more preferably in the range between 0.1 μm and 0.5 μm.

Then, as shown in FIG. 5E and the step S64 of FIG. 6, the photoresist layer 33 and the portion of the seed layer 32 uncovered by the conductive layers 36 and 37 (i.e. the portion of the seed layer 32 covered by the photoresist layer 33) are removed. Consequently, a first metal line microstructure 38 and a second metal line microstructure 39 are produced. In case that the photoresist layer 33 is the wet film photoresist layer, the photoresist layer 33 may be removed by an etching process. In case that the photoresist layer 33 is the dry film photoresist layer, the photoresist layer 33 may be removed by a stripping process. Moreover, the portion of the seed layer 32 uncovered by the conductive layers 36 and 37 are removed by an etching process, but is not limited thereto. In this embodiment, the line width of the first metal line microstructure 38 is substantially equal to the first width W1 of the first trench 34, and the line width of the second metal line microstructure 39 is substantially equal to the second width W2 of the second trench 35. That is, the line width of each of the first metal line microstructure 38 and the second metal line microstructure 39 is in the range between 1 μm and 20 μm, preferably in the range between 1 μm and 5 μm, and more preferably smaller than 3 μm. In case that the line width of the first metal line microstructure 38 is controlled to be in the range between 1 μm and 5 μm (more preferably smaller than 3 μm) according to the width of the trench 14, when the first metal line microstructure 38 is applied to the metal line (or metal mesh) of a visible touch zone of a touch panel, the transmittance and the invisibility of the metal line are both enhanced. In case that the line width of the second metal line microstructure 39 is controlled to be in the range between 1 μm and 20 μm (more preferably in the range between 5 μm and 20 μm), the second metal line microstructure 39 may be applied to the metal line of the non-touch zone of the touch panel. In other words, the second metal line microstructure 39 may be used as the wiring part on the peripheral region of touch panel. The height of the first metal line microstructure 38 is substantially equal to the depth of the first trench 34 (e.g. in the range between 0.1 μm and 20 μm), and the height of the second metal line microstructure 39 is substantially equal to the depth of the second trench 35 (e.g. in the range between 0.1 μm and 20 μm). The height of the first metal line microstructure 38 and the height of the second metal line microstructure 39 may be determined according to the requirements of the impedance value, thereby increasing the stability of the metal line.

FIG. 7 schematically illustrates the metal lines formed by the manufacturing method according to the third embodiment of the present invention. As shown in FIG. 7, the first metal line microstructure 38 and the second metal line microstructure 39 are located at the visible touch zone and the non-touch zone of the touch panel 1, respectively. The line width of the first metal line microstructure 38 is controlled to be in the range between 1 μm and 5 μm (more preferably smaller than 3 μm). Consequently, the line width is tiny, and the transmittance and the invisibility of the metal line are both enhanced. The line width of the second metal line microstructure 39 is controlled to be in the range between 5 μm and 20 μm. Consequently, the second metal line microstructure 39 may be used as the wiring part on the peripheral region of touch panel 1. Please refer to FIGS. 5A˜5E, 6 and 7 again. The first metal line microstructure 38 and the second metal line microstructure 39 may be formed on the substrate in the same fabricating step. In other words, the first metal line microstructure 38 and the second metal line microstructure 39 may be used as the metal line of the visible touch zone and the wiring part of the non-touch zone of the touch panel 1, respectively. Consequently, the fabricating procedures of the touch panel 1 are simplified, and the fabricating cost of the touch panel 1 is reduced.

From the above descriptions, the present invention provides a method of manufacturing microstructures of metal lines. By the manufacturing method of the present invention, the metal line is thinner, the fabricating cost is reduced, and the transmittance and the invisibility of the metal line are both enhanced. Moreover, since the line width of the metal line can be precisely controlled to be smaller than 5 μm, the yield of the product is increased, and the oxidation of the metal line is minimized. Moreover, since the metal line of the visible touch zone and the wiring part of the non-touch zone of the touch panel can be simultaneously formed on the substrate in the same fabricating step, the fabricating procedures of the touch panel are simplified, and the fabricating cost of the touch panel is reduced.

While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures. 

What is claimed is:
 1. A method of manufacturing a metal line microstructure, the method comprising steps of: (a) providing a substrate; (b) forming a seed layer on a surface of the substrate; (c) forming a photoresist layer on a surface of the seed layer, and performing a photolithography and etching process to form a trench in the photoresist layer, wherein the trench has a specified width; (d) performing an electroplating process to fill a conductive layer into the trench; and (e) removing the photoresist layer and a portion of the seed layer uncovered by the conductive layer, so that the metal line microstructure is produced.
 2. The method according to claim 1, wherein the substrate is a transparent substrate, a flexible substrate or a flexible transparent substrate.
 3. The method according to claim 1, wherein a thickness of the seed layer is in a range between 5 nm and 100 nm, and the seed layer is made of metal or metal alloy, wherein the metal or the metal alloy is selected from a Cr/Au metal film, a Ti/Au metal film, a Ti/Cu metal film, a Cu/Cu metal film or a Ti—W/Au metal film.
 4. The method according to claim 1, wherein the specified width of the trench is in a range between 1 μm and 20 μm, and the trench has a specified depth in the range between 0.1 μm and 20 μm.
 5. The method according to claim 4, wherein the specified width of the trench is in a range between 1 μm and 5 μm, and the specified depth of the trench is in a range between 0.1 μm and 2 μm.
 6. The method according to claim 4, wherein the specified width of the trench is smaller than 3 μm.
 7. The method according to claim 1, wherein in the step (c), a portion of the seed layer is exposed, wherein in the step (d), the conductive layer is in contact with the exposed portion of the seed layer.
 8. The method according to claim 1, wherein the conductive layer is made of copper, gold, silver, aluminum, tungsten, iron, nickel, chromium, titanium, molybdenum, indium, tin, or a combination thereof.
 9. The method according to claim 1, wherein a width of the conductive layer is determined according to the specified width of the trench, wherein a thickness of the conductive layer is in a range between 0.1 μm and 2 μm.
 10. A method of manufacturing a metal line microstructure, the method comprising steps of: (a) providing a substrate; (b) forming a seed layer on a surface of the substrate; (c) forming a photoresist layer on a surface of the seed layer, and performing a photolithography and etching process to form a trench in the photoresist layer, wherein the trench has a specified width; (d) performing an electroplating process to fill a conductive layer into the trench; (e) filling an anti-oxidation layer into the trench and forming the anti-oxidation layer on the conductive layer; and (f) removing the photoresist layer and a portion of the seed layer uncovered by the conductive layer, so that the metal line microstructure is produced.
 11. The method according to claim 10, wherein the anti-oxidation layer is an anti-oxidation metal layer, and the anti-oxidation layer contains phenolic resin, photosensitive compounds, organic colored polymer dyes, inorganic colored dyes and solvent.
 12. A method of manufacturing a metal line microstructure, the method comprising steps of: (a) providing a substrate; (b) forming a seed layer on a surface of the substrate; (c) forming a photoresist layer on a surface of the seed layer, and performing a photolithography and etching process to form a first trench and a second trench in the photoresist layer, wherein the first trench has a first width, the second trench has a second width, and the second width is larger than the first width; (d) filling a conductive layer into the first trench and the second trench; and (e) removing the photoresist layer and a portion of the seed layer uncovered by the conductive layer, so that a first metal line microstructure and a second metal line microstructure are produced.
 13. The method according to claim 12, wherein the first width of the first trench is in a range between 1 μm and 5 μm, and the second width of the second trench is in a range between 5 μm and 20 μm, wherein a line width of the first metal line microstructure is substantially equal to the first width, and a line width of the second metal line microstructure is substantially equal to the second width. 